Copter: disable centrifugal force correction when disarmed

ArduCopter/Parameters.pde

@@ -966,6 +966,8 @@ static void load_parameters(void)
     if (!ahrs.gps_gain.load()) {
         ahrs.gps_gain.set_and_save(1.0);
     }
+    // set gps_gain to zero, it will be set back to 1 as part of the arming process
+    ahrs.gps_gain.set(0);
 
     // setup different AHRS gains for ArduCopter than the default
     // but allow users to override in their config

ArduCopter/motors.pde

@@ -144,6 +144,9 @@ static void init_arm_motors()
     ahrs2.set_fast_gains(false);
 #endif
 
+    // enable gps velocity based centrefugal force compensation
+    ahrs.gps_gain.load();
+
     // finally actually arm the motors
     motors.armed(true);
 
@@ -209,6 +212,9 @@ static void init_disarm_motors()
 #if SECONDARY_DMP_ENABLED == ENABLED
     ahrs2.set_fast_gains(true);
 #endif
+
+    // disable gps velocity based centrefugal force compensation
+    ahrs.gps_gain.set(0);
 }
 
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